Spinal implant devices are commonly used to correct or stabilize the position of vertebral segments in a patient's back. Such correction may be necessary as a result of accidents, degenerative diseases, etc.
U.S. Pat. No. Re. 36,221 to Breard et al. discloses an intervertebral stabilizer which includes one or more flexible or semi-elastic ligaments. The stabilizer may be implanted on one side only or on both sides of the spines of the vertebrae concerned, or on the front face or rear face thereof. Screws may be implanted in corresponding vertebrae for retaining the ligament therebetween. Each of the screws may further include a detachable, threaded cap for securing the ligament to the screw.
Another intervertebral stabilizer device for attachment to two vertebrae is disclosed in U.S. Pat. No. 5,375,823 to Navas. This stabilizer includes a housing defining an internal chamber, a piston within the housing, and first and second elastic dampers within the chamber to dampen movement of the piston. The volume and characteristics of these dampers may be varied to provide more or less resistance. Further, the stabilizer also includes a rod extending from each end of the chamber, each of which terminates in a ball joint. A screw is mounted in each of the two vertebrae, and each screw has a head which receives the ball joints and pivots with respect thereto. A stated goal of this device is to relieve an injured disk when it withstands compression and traction forces.
An intervertebral locking device is disclosed in U.S. Pat. No. 5,360,430 to Lin which includes a bottom base, a bracing member, a top base, and at least one adjusting arm. According to one embodiment of the invention, the bracing member may be a spring body made of an elastic material. The locking device may be implanted within the spinal column.
U.S. Pat. No. 5,616,142 to Yuan et al. discloses a vertebral fixation device which includes a receiving piece, a sliding piece, and a plurality of fastening elements for connection of the two. More specifically, the receiving piece is provided with two sliding grooves in which the sliding piece is slidably received.
Furthermore, U.S. Pat. No. 6,136,002 to Shih et al. discloses an anterior spinal fixation system including upper and lower vertebral plates with a pair of parallel rods connected therebetween. More particularly, each vertebral plate includes a staple vertebral plate attached to a respective vertebra by two screws, and a universal cover plate for securing the rods between itself and the staple vertebral plate. The universal cover plates are connected to the staple vertebral plates with locking nuts.
Despite the advantages of such spinal implant devices, further operational and adjustment features may be desirable in certain applications.